Horse News & Views - June 2003

Ministry of Agriculture, Food and Rural Affairs

Ontario Association of Equine Practitioners

• Often horse owners allow horses to graze on pastures too early in the spring. The first grazing should occur when the plants are three to four inches high and the horses are not punching holes in the soil. Horses should be rotated to a new paddock every five to six days to prevent them from grazing too close to the ground. The plants should not be grazed below two to three inches. This will require the availability of a large number of paddocks. Temporary paddocks can be created by using electrical fence.

• Mules are not always sterile! The crossing of a horse with 64 chromosomes and a donkey with 62 is thought to produce a sterile mule with 63 chromosomes. However, a report from Morocco indicates that a mule mare produced a foal with 62 chromosomes. The cells of the mule mare were a mosaic, some carrying 63 chromosomes while others carried 62. The foal is believed to be fathered by a donkey. This is the fourth female mule confirmed to be fertile. (Kay G. Vet Record 2002; 152 (3, Jan. 18))

• In Ontario, rural landowners who have a pond or dug-out that is wholly contained on their property, with no outflow or connection in any way to surface waters, can apply the larvicide Bti (Bacillus thuringiensis israeliensis). This naturally occurring bacterium provides the most effective control at certain stages of a mosquito's life cycle, so repeated applications of this larvicide are necessary to achieve effective mosquito control. Bti is available in a granular form from local feed and hardware outlets, garden centres and pest control companies. Products currently registered, available in Canada and classified for use in Ontario as Schedule 3 products include AquaBac 200G and VectoBac 220G. Products sold in the US such as slow release dunks or pucks are not registered in Canada.

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